A commonplace type of zipper comprises two rows of inter-lockable elements (or teeth) and a slider which can be moved in an opening direction to open the zipper and in a closing direction to close the zipper.
Examples of such zippers are disclosed in U.S. Pat. No. 2,599,078 and U.S. Pat. No. 5,255,418. Each of these documents discloses a zipper that has a slider which includes an automatic locking mechanism that serves to prevent unintentional movement of the slider in the opening direction. In each case, the locking mechanism includes a control member that is moveable from a locking position, in which movement of the slider in the opening direction is prevented, to an unlocking position. Movement of the control member from the locking position to the unlocking position is achieved by application of a force to the control member via a pull tab which physically engages the control member. In both U.S. Pat. No. 2,599,078 and U.S. Pat. No. 5,255,418, the control member has a pin, formed integrally with the control member, the pin interposing between the elements of the zipper to achieve the locking.
Other zippers have sliders that are provided with security locking mechanisms incorporating combination locks or key operated locks and which allow the slider to be locked to prevent unauthorised opening of the zipper.